Polarization Effects on Magnetic Resonances in Ferroelectric Potassium Tantalate

摘要

Electric field effects on electron paramagnetic resonances (EPR) associated with Fe(3+) impurity ions in the perovskite ferroelectric KTaO3 are presented and discussed. A large effect (D = 0.003/cm for E = 14 kv/cm) was predicted and observed at 4.2 degrees K. The EPR angular dependence data for the Fe(3+) ion in a cubic environment are interpreted in terms of appropriate spin Hamiltonian parameters. The result is alpha = (345=10) x 0.0001/cm and g = 1.99 = 0.01. We also reported EPR spectra for Fe(3+) ions that have a neighboring oxygen vacancy, and also for Fe(5+), Mn, and Cr. Evidence for covalent bonding of magnetic impurities to the KTaO3 lattice is given. Optical absorption spectra associated with Fe, Mn, and Co impurities are also reported. A brief investigation was made of transport properties of slightly reduced, electrically conducting (n-type) samples of KTaO3. There is a strong temperature-dependent Hall mobility (28 sq cm/volt sec at room temperature and at least 63,000 sq cm/volt sec at 4.2K). A method for growing fairly large (about 1 cu cm) and good quality single crystals of KTaO3 is described.